Endoscopy in the medical field allows internal features of the body of a patient to be viewed without the use of traditional, fully-invasive surgery. FIGS. 1A and 1B collectively illustrate an endoscopic imaging system such as commonly used in the medical field. FIG. 1A generally illustrates the image generation and display components of the system, while FIG. 1B illustrates the data acquisition components of the system. The data acquisition components include an endoscope 2, a camera 3, and a coupler 6. The endoscope 2 has a distal end, i.e., the tip of the scope shaft 15, and a proximal end, i.e., the housing 14, which is connected to the camera 3 by the coupler 6. The camera 3 acquires color video image data of internal features of a body through an optical pathway (a system of lenses, for example) in the endoscope 2. FIG. 1A shows the image generation and display components of the system, which include a camera control unit (CCU) 9, a light source unit 7, a monitor 13, a video recorder 10, and a printer 11, which are stored on a mobile cart 12. Various other system configurations are also possible.
High-intensity light is provided to the endoscope 2 by the light source unit 7 through a flexible light conduit 8, which may be a fiber optic cable. An external light port (e.g., light post 4) that extends from the housing 14 of the endoscope 2 enables the light conduit 8 to attach to the endoscope 2. Certain camera functions can be controlled from the camera control unit (CCU) 9. The camera 3 is coupled to the camera control unit (CCU) 9 by a flexible transmission line 5. The transmission line 5 conveys power to the camera 3, video image data from the camera 3 to the CCU 9, and various control signals bi-directionally between the camera 3 and the CCU 9. Image data received by the CCU 9 from the camera 3 are processed and converted to video images by the CCU 9, which are displayed on the monitor 13, and if desired, recorded by the video recorder 10 and/or used to generate static images that can be printed by printer 11.
A typical light source unit 7 is comprised of a light bulb, a ballast power supply, control circuitry and cooling fans. This system is extremely inefficient and must generate extremely bright light to compensate for the distance the light rays must travel and the losses experienced through the system. This system may also cause infrared heat energy to be transmitted into the patient, which can create hazardous conditions during the surgery. Furthermore, the color content of the light cannot be controlled, which can adversely affect image quality, and the light cable that connects the light source to the scope is cumbersome.
Using light emitting diodes (LEDs) as a light source for an endoscope has been proposed. Because LEDs are small in size, they can be integrated into an endoscope to bring the light source closer to the surgical site.
For example, there are proposals to place multiple LEDs as a light source into the tip or annular area of the scope shaft of an endoscope. There are, however, at least two problems with this kind of design. First, the space inside the tip or annular area of the scope shaft is relatively small. Therefore, very few LEDs can be integrated into the endoscope. Second, because endoscopes can come in different sizes, an LED based light source must be specifically designed for a particular endoscope size if it is placed in the tip or annular area of the scope shaft.
Current LEDs available are usually pre-packaged single diode assemblies. It is difficult to obtain the light output required for endoscopic applications in a compact space, as the packaging is often on the order of 50× the size of the LED. If multiple LEDs are placed on one circuit board, their proximity becomes limited by required heat dissipation. As heat increases, lifetime of the LED dramatically decreases. Reducing the supplied power can reduce the thermal load, but decreases the light output.
Also, different doctors prefer different color temperatures for illumination during an endoscopic procedure. It is desirable to have a light source unit that allows a doctor to adjust the color temperature of its light to the doctor's preferred condition during an endoscopic procedure. In addition, at a surgical site within a patient's body, some anatomical surfaces may be closer to the endoscope tip, where light is emitted, than other surfaces; as such, some portions of the image may become overly bright or overly dark. What is needed, therefore, is a light source unit for an endoscopic imaging system, which overcomes these problems.